Koto Battle: Tengai no Moribito (コトバトル－天外の守人－) is the debut video game developed by Nintendo's second-party developer, AlphaDream. It was released in Japan on March 9, 2001 for the Nintendo Game Boy Color.

The game progresses by defeating other characters in kotodama card battles. Most battles are fought against wild monsters encountered randomly in the wilderness, or generic kotodama battlers placed throughout the game map. Certain battles cannot be avoided because they are essential to the game's story. When the player enters a battle, the right side of the screen is the player's field, and the opposite side is the enemy's field. As a kotodama battler, the player has the ability to summon up to three friendly monsters to assist in battle, each placed on the top, mid, and lower sections of the screen.

There are four options available in the battle menu; "Use kotodamas," "Kotodama history," "Defend," and "Escape." Items cannot directly be used by the player, and battles are fought out entirely through the use of kotodamas. Turns are determined by the "timecost" assigned to each type of kotodama or monster, and begin when the other side's timecost goes to zero. Kotodama battlers begin each battle with a timecost of 5, and monsters may have a timecost shorter or longer than that according to their type.